The invention relates to an optical rotary transmitter having the features of the preamble of claim 1. Such a rotary transmitter may be part of a rotary coupling, for example, or some other device having rotationally movable parts spaced a distance apart from one another and permits unidirectional or bidirectional transmission of optical signals between parts that are rotatable relative to one another independently of their rotational position and angular velocity. The wavelength range may extend from long-wavelength IR radiation to short-wavelength UV radiation. The terms “light” and “optical” are to be understood in this sense below.
Such optical rotary transmitters are known from DE 603 14 028 T2 and GB 2 247 089 A. They permit high signal transmission reliability, regardless of the angular velocity of the parts that are rotatable in relation to one another, and use commercial semiconductor transmitter and receiver bit rates of up to 10 Gbit/s. However, multichannel operation is possible only when using time multiplex methods or wavelength multiplex methods.
JP 62-028704 A discloses an optical rotary transmitter having two parts that are spaced a distance apart from one another and rotate relative to one another about a common central axis, the first part of which has collimators arranged tightly in a circle around this central axis and the second part has second collimators that are spaced further apart radially from this central axis, the parallel beam bundles being focused on the first collimators by a Fresnel lens.
JP59-017526 A discloses a scanner for rotary scanning of the beam exit surfaces of waveguide fibers arranged on the circumference of a circle. This purpose is served by another waveguide fiber having a longitudinal axis running through the midpoint of the circle, rotating about same and having an end bent at an angle by the amount of the midpoint distance of the beam exit surfaces of the first waveguide fibers.
US-A-4 943 137 discloses a rotary transmitter whose light is directed by an optical transmitter, which is assigned to one of the two parts that is rotatable in relation to the others, via optical fibers and collimators to an optical coupling module and from there further to an optical receiver, which is assigned to the other rotatable part. The coupling module serves the purpose of derotation of the light, so it rotates at half the angular velocity of the two parts that are rotatable in relation to one another. Consequently, this design is very complex.
US-A-4 027 945 discloses a rotary transmitter, in which the optical signals of a transmitter assigned to the first of the parts rotatable in relation to one another are fed into a fiber bundle. This fiber bundle is arranged in a circle about the axis rotation; likewise a similar fiber bundle is arranged on the second part which includes an optical receiver. This requires a large number of optical fibers, i.e., waveguide fibers.
AS-4-6 128 426 describes a rotary transmitter in which light from an optical transmitter, for example, which rotates together with the first part, is transmitted to a plurality of optical receivers or detectors arranged in a circle on the second part. This rotary transmission requires angle decoding of the relative positions of the rotary parts to one another.
DE-A-10 2008 030 187 describes a rotary transmitter in which an optical transmitter assigned to the first part feeds optical signals into a waveguide on the second part. The waveguide therefore has a specially processed surface, which permits this light signal feed. Such waveguides are not available commercially and are therefore expensive.
DE-A-10 2006 054 052 describes a rotary transmitter having two light-conducting hollow bodies coaxial with one another into which light signals from a transmitter are fed by means of waveguides distributed around the circumference of the one hollow body, the signals being emitted through the end face thereof in the direction of the end face of the other hollow body and output by the same principle via waveguides of the other part and sent to a receiver. With this design, there is high signal attenuation due to uniform distribution of the signals over the entire circumference of the hollow bodies.